Oklahoma Gas & Electric (OG&E) has requested a construction permit from the Oklahoma Department of Environmental Quality for the coal-fired Sooner plant to add low-NOX burners (LNB) and overfire air (OFA) to Units 1 and 2 to reduce emissions of NOX to meet Best Available Retrofit Technology (BART) requirements.
The DEQ on Nov. 27 began taking public comment on the draft permitting for this project.
“OG&E proposes the installation of LNB/OFA technology on Units 1 and 2 to reduce nitrogen oxide (NOX) emissions from the Sooner Generating Station,” the DEQ said. “LNB and OFA are two forms of combustion control that have been combined in a single technology to reduce NOX emissions from pulverized coal fired units. NOX, primarily in the form of NO and NO2, is formed during combustion by two primary mechanisms; thermal NOX and fuel NOX. Thermal NOX results from the dissociation and oxidation of nitrogen in the combustion air. The rate and degree of thermal NOX formation is dependent upon oxygen availability during the combustion process and is exponentially dependent upon the combustion temperature. Fuel NOX, on the other hand, results from the oxidation of nitrogen organically bound in the fuel. Fuel NOX is the dominant NOX producing mechanism in the combustion of pulverized coal and typically accounts for 75 to 80 percent of total NOX.”
OFA works by reducing the excess air in the burner zone, thereby enhancing the combustion staging effect of the LNBs and further reducing NOX emissions, DEQ said. Residual unburned material, such as carbon monoxide (CO) and unburned carbon that inevitably escapes the main burner zone, is subsequently oxidized as the OFA is added.
OG&E’s project contractor has guaranteed emission results under specified test conditions of 0.15 lb/MMBTU NOx and 0.37 lb/MMBTU of CO for each unit, the agency wrote.
The Sooner facility currently uses No. 2 fuel oil as a start-up fuel and sub-bituminous low-sulfur Powder River Basin coal as the primary fuel. In addition, OG&E combusts small amounts of waste products from Sooner and other OG&E facilities in the boilers.
Both Units 1 and 2 can potentially combust about 300 tons per hour of coal to produce 3.8 million pounds per hour of steam each. Both boilers were manufactured by Combustion Engineering with a design maximum heat input of 5,116 million BTUH and a nominal 550 MW output. During the combustion process, the fly ash is collected by the electrostatic precipitators. The precipitators are designed to remove 99.52% of the fly ash from the flue gas.
NOx controls not an issue in regional haze fight with EPA
OG&E parent OGE Energy (NYSE: OGE) said in its Nov. 7 Form 10-Q report that the need for NOx controls under BART is being driven, in part, by a contested 2010 State Implementation Plan (SIP) under the regional haze rule of the U.S. Environmental Protection Agency.
“The Oklahoma SIP included requirements for reducing emissions of NOX and SO2 from OG&E’s seven BART-eligible units at the Seminole, Muskogee and Sooner generating stations,” said the Form 10-Q. “The SIP also included a waiver from BART requirements for all eligible units at the Horseshoe Lake generating station based on air modeling that showed no significant impact on visibility in nearby national parks and wilderness areas. The SIP concluded that BART for reducing NOX emissions at all of the subject units should be the installation of low NOX burners with overfire air (flue gas recirculation was also required on two of the units) and set forth associated NOX emission rates and limits. OG&E preliminarily estimates that the total capital cost of installing and operating these NOX controls on all covered units, based on recent industry experience and past projects, will be approximately $100 million.”
With respect to SO2 emissions, the SIP included an agreement between the Oklahoma DEQ and OG&E that established BART for SO2 control at four coal-fired units at Sooner and Muskogee as the continued use of low-sulfur coal (along with associated emission rates and limits). The SIP specifically rejected the installation of dry scrubbers as BART for SO2 control from these units because the state determined that dry scrubbers were not cost effective.
The Form 10-Q added: “On December 28, 2011, the EPA issued a final rule in which it rejected portions of the Oklahoma SIP and issued a [Federal Implementation Plan] in their place. While the EPA accepted Oklahoma’s BART determination for NOX in the final rule, it rejected Oklahoma’s SO2 BART determination with respect to the four coal-fired units at the Sooner and Muskogee generating stations. The EPA is instead requiring that OG&E meet an SO2 emission rate of 0.06 pounds per MMBtu within five years. OG&E could meet the proposed standard by either installing and operating Dry Scrubbers or fuel switching at the four affected units. OG&E estimates that installing Dry Scrubbers on these units would include capital costs to OG&E of more than $1.0 billion. OG&E and the state of Oklahoma filed an administrative stay request with the EPA on February 24, 2012. The EPA has not yet responded to this request. OG&E and other parties also filed a petition for review of the FIP in the U.S. Court of Appeals for the Tenth Circuit on February 24, 2012 and a stay request on April 4, 2012. On June 22, 2012, the U.S. Court of Appeals for the Tenth Circuit granted the stay request.”
OGE noted that the stay will remain in place until a decision on the petition for review is complete, which will delay the implementation of the regional haze rule in Oklahoma. On June 15, 2012, OG&E, the state of Oklahoma and other parties filed a court brief in support of the petition for review of the final regional haze rule of the EPA. The briefing by all parties was completed in October 2012.